MEP Candollea 59/2

Orobanchaceae of the Arabian Peninsula M. J. Y. FOLEY ABSTRACT FOLEY, M. J. Y. (2004). Orobanchaceae of the Arabian Peninsula. Candollea 59: 231-254. In English, English and French abstracts. Based mainly upon preserved herbarium material collected from within the Arabian peninsula, the taxonomy, ecology and distribution of members of the Orobanchaceae are described; this includes two new species: Orobanche perangustata M. J. Y. Foley and O. muteliformis M. J. Y. Foley. Three species of Cistanche and eleven other species of Orobanche have been recognized. RÉSUMÉ FOLEY, M. J. Y. (2004). Les Orobanchacées de la Péninsule arabique. Candollea 59: 231-254 . En anglais, résumés anglais et français. Basées principalement sur le matériel conservé en herbier, la taxonomie, l’écologie et la distribu - tion des Orobanchacées de la Péninsule arabique sont présentées. Sont inclues deux nouvelles espèces: Orobanche perangustata M. J. Y. Foley et O. muteliformis M. J. Y. Foley. Trois espèces du genre Cistanche et onze espèces du genre Orobanche sont reconnues. KEY-WORDS: OROBANCHACEAE – Arabian Peninsula The family Orobanchaceae has been poorly studied in the Arabian peninsula. This is mainly due to a general lack of preserved specimens from what is a vast, often inhospitable, and rarely visited terrain, covering an area of approximately three million square kilometres. However, material is relatively well represented in a few herbaria and especially so in K, BM and E and this, together with that in ON, SQUH and elsewhere, has been examined. Collections made by individual field botanists figure regularly within this family and have been the basis upon which much of the following account has been prepared. Of these I. S. Collenette, J. P. Mandaville, A. G. Miller and J. R. I. Wood merit special mention. There is still a great deal of investigative work to be carried out into the taxonomy of members of the Orobanchaceae of the Arabian peninsula; no doubt, other taxa will be recorded as botanical exploration is extended. Also, future molecular phylogenetic studies on the lines of that carried out elsewhere by SCHNEEWEISS & al. (2004) should help to clarify the taxonomy further. It is hoped that this account will, at least, act as a basis for future work. CODEN: CNDLAR CONSERVATOIRE ET JARDIN 59(2) 231 (2004) © ISSN: 0373-2967 BOTANIQUES DE GENÈVE 2004 232 CANDOLLEA 59, 2004 Orobanchaceae Annual, biennial or perennial herbs, lacking chlorophyll and completely parasitic upon the roots of a wide range of (usually) dicotyledonous plants. Stems erect, fleshy, simple or branched. Leaves scale-like, alternate, numerous. Inflorescence consisting of a usually many-flowered terminal raceme or rarely single-flowered, the flowers subtended by a single bract, with or without two lateral bracteoles. Calyx tubular or campanulate or ± divided into two lateral segments, the segments either further divided into (usually) two teeth, or entire. Corolla tubular, infundibu - liform, campanulate or obconical, comprising five ± equal and regularly distributed lobes or else distinctly two-lipped with two upper and three lower lobes. Stamens four, didynamous, with a fifth reduced to a staminode or absent; filaments usually inserted towards the base of the corolla. Ovary superior comprising (usually) two fused carpels and a single locule; placentation axile; ovules numerous; style single, stigma two-lobed. Fruit a loculicidal capsule dehiscing by two valves. Seed numerous, very small; testa rugose or reticulate-foveolate. The family is traditionally maintained separately from the Scrophulariaceae but such a delimitation is questionable. There are about 14 genera world-wide, distributed mainly in the temperate regions of the northern hemisphere where Orobanche is the largest genus. Notes: This is a taxonomically difficult family of obligate root parasites. Members of the genera Cistanche and Orobanche , because of their fleshy, succulent and achlorophyllous nature, preserve poorly so that important taxonomic characters, including colour, are often lost. As with many parasitic plant genera, morphological reduction has meant that useful diagnostic characters are limited. Of these, the most important include inflorescence morphology (density, corolla attitude etc.), calyx shape, corolla colour, shape and size, corolla lobe denticulation and ciliation, distribution and type of pilosity on the filaments, height of insertion of the filaments above the base of the corolla, and the colour and degree of separation of stigma lobes. Frequently, a combination of these characters is necessary to satisfactorily separate closely related taxa. Since the colour of the corolla and stigma lobes are most useful diagnostic characters, the importance of recording these when collecting cannot be over-emphasised. Unfortunately, up to present such information is lacking on many herbarium collections although most of those collected by Collenette are well documented in this way. The range of dimensions given below are those typical of most plants. However, even within a single population, plants may vary appreciably in respect to these characters. Dimensions for stem width are measured immediately below the inflorescence whilst those for corolla length are taken in a direct line from the corolla base to the tip of the upper lip. There is sometimes uncertainty as to whether individual taxa are annual, biennial or perennial and it is possible that in certain cases all these conditions may variously apply depending upon the host or on environmen - tal influence. However, those species which parasitise annuals such as crop plants may reasonably be assumed to also be annual. Specimens of members of this family, when preserved for the herbarium, frequently become embrittled and damage easily; they also lose many important characters after pressing. Due to this, their value is often reduced and can cause a problem in identification. For these reasons, it is important that a full description of the plant should be recorded when making new collections and should include the shape and colour of the corolla, the height of insertion of the filaments above the corolla base, the type and distribution of filament pilosity and the colour of the stigma lobes. All this information should be noted on the label. Failure to do so will, in many cases, mean that the specimen is undeterminable and therefore its worth greatly diminished. The addition to the herbarium sheet of a good colour photograph can also be helpful. Wherever possible, the physical attachment between the parasite and the roots of the host should be established by careful excavation. OROBANCHACEAE OF THE ARABIAN PENINSULA 233 Suggested modern floristic literature (References cited in the text are at the end of this article) ANON. (1983). Wild Plants of Qatar. Arab Organization for Agricultural Development. BOULOS, L. (1988). The Weed Flora of Kuwait. Kuwait City. CHAUDHARY, S. A. & M. A. ZAWAWI (1983). A Manual of Weeds of Central and Eastern Saudi Arabia. CHAUDHARY, S. A. (1987). Weeds of Saudi Arabia and the Arabian Peninsula. Riyadh. CHAUDHARY, S. A. & L. J. MUSSELMAN (2001). Orobanchaceae. In: CHAUDHARY, S. A., Flora of the Kingdom of Saudi Arabia 2(2): 514-523. Riyadh COLLENETTE, S. (1985). An Illustrated Guide to the Flowers of Saudi Arabia . London. COLLENETTE, S. (1999). Wildflowers of Saudi Arabia. Riyadh. CORNES, M. D. & C. D. CORNES (1989). The Wild Flowering Plants of Bahrain. An Illustrated Guide. London. DAOUD, H. S. & A. AL-RAWI (1985). Flora of Kuwait 1. London. GHAZANFAR, S. A. (1992). An Annotated catalogue of the Vascular Plants of Oman and their Vernacular Names. Scripta Bot. Belg. 2. MANDAVILLE, J. P. (1990). Flora of Eastern Saudi Arabia. London. MIGAHID, A. M. (1978). Migahid and Hammouda’s Flora of Saudi Arabia 1. Riyadh. WESTERN, A. R. (1989). The Flora of the United Arab Emirates. An Introduction . Dubai. WOOD, J. R. I. (1997). A handbook of the Yemen Flora . Kew. Key to genera 1. Corolla ± actinomorphic, subequally 5-lobed ................................................... 1. Cistanche 1a. Corolla zygomorphic, 2-lipped, the upper lip bilobed, the lower 3-lobed ....... 2. Orobanche 1. Cistanche Hoffmanns. & Link Parasitic, usually perennial herbs to 100 cm high. Stem robust, simple. Leaves numerous, usually imbricate below. Inflorescence , a dense terminal spike, many-flowered, each flower with a single bract and (in our species) two lateral bracteoles adnate to the campanulate, usually 5-lobed calyx; calyx lobes obtuse, rounded. Corolla ± regular, tubular, campanulate or ± obconical with five subequal, patent lobes, and often with two prominent bosses in the throat of the corolla. Stamens included; style curved near apex, stigma robust, subentire. Capsule ovoid, seeds subglobose, very small. Note: At least 20 species have been described. These are frequent in north Africa and western and central Asia but only occasional in southern Europe. All are plants of sandy, usually saline habitats, either coastal or else inland in steppe or desert terrain and are parasitic on various hosts. However, the taxonomy of the genus is poorly understood and in urgent need of further investigation. Difficulties in the study of the genus arise because of the difficulty in determining meaningful taxonomic characters in plants which preserve so poorly, so that much of the currently available herbarium material is undeterminable. Remoteness of many populations, their presence in a hot, arid environment, and possible morphological variation across the geographical range

Load more